Because we already have a rough estimate of the amount of gold available for mining on the earth. Current gold value is determined by a combination of demand, currently mined supply, and the potentialy available gold on the earth.

Now immagine the amount of potential gold on the planet becoming infinite.

Doesn't even have to be that complicated, this is something that has always irked me about Superhero Worlds. Endeavor and Todoroki, or literally any other hero with a heat quirk for that matter, is more than capable of solving the world's energy crisis. Depending on the temperature they can reach, a significant about of energy could be generated simply by them heating water within a sealed environment, and allowing the steam from the heated water to push a piston at the top of this sealed environment. That's exactly how Nuclear Energy generates electricity, thing get hot make water go hot become gas push piston. Practically every power station is just a glorified giant teapot.

I gotta assume quirks that produce heat are pretty common, doesn't always have to be fire, I'm sure Bakugo would be capable too. So there are dudes with heat quirks all over the world that could be solving the energy crisis, but aren't. Buncha lazy faggots tbh fam